Die-bowl assembly



Sept. 15, 1953 E, MEAKlN 2,652,007

DIE-BOWL ASSEMBLY Filed Oct. 21, 1948 2 Sheets-Sheet 1 Fig. .l.

INVENTOR. EDGAR IV. MFA/(NV BY mfm HIS ATTORNEYS E. N. MEAKIN DIE-BOWL ASSEMBLY Sept. 15, 1953 2 Sheets-Sheet 2 Filed Oct. 21, 19 48 INVENTOR. 506%? A/. ms'A/mv BY mym Patented Sept. 15, 1953 UNITED STATES PATENT OFFICE DIE-BOWL ASSEMBLY Edgar N. Meakin, Hillsborough, Calif.

Application October 21, 1948, Serial No. 55,701

1 Claim. 1

My invention relates to extrusion mills, and more particularly to a die-bowl assembly for pellet mills adapted for the compaction of material in the formation of pellets.

One of the problems connected with the operation of pellet mills is to obtain uniform extrusion results throughout the operating area of the die. invariably, the extrusion of material through the die holes at the inner and outer peripheries of the operating area of the die is not as uniform and efiicient as with the intermediate die holes, with the result that the pellets formed through such peripheral holes are short and irregular.

A further drawback to such non-uniform functioning of the extrusion assembly is the nonuniform wearing of the die.

The underlying cause of such non-uniform results is not apparent to one observing the operation of the machine, for the die and the pressure contacting portion of the extrusion means are buried in the material to be compacted and extruded, and just what is taking place between the extrusion components is not open to view.

I have found that by providing a wall bordering each side of the operating area of the die, as determined by the path of travel of the extrusion means thereover, a uniform extrusion of pellets across the die may be realized, resulting in an unexpected increase in the productive capacity of the mill of the order of 65% depending largely upon the die hole pattern employed. At the same time, wear on the die can be caused to be uniform, while the life of the die is also thereby increased.

For a description of my invention in its preferred form, reference will be had to the accompanying drawings wherein- Figure 1 is a view in section through the pertinent portions of a pellet mill;

Figure 2 is an enlarged view of a detail of Figure 1;

Figure 3 is a plan View of the die-bowl assembly of Figure 1 with the position of the rollers indicated in phantom.

Referring to the drawings for the details of apparatus for the carrying out of my invention, the mill in general, may comprise a base frame I supporting an inwardly sloping circular bowl 3 having an out-turned lower edge 5 from which a die clamp I such as illustrated and described in Meakin Patents 2,075,450 of March 30, 1937, and 2,124,744 of July 26, 1938, is suspended to engage and support the outer edge of a ring die 9.

A centrally mounted sleeve I I, supported in any conventional manner in the upper portion of the mill, as by a thrust bearing 13, carries at its lower end, as by a nut I5 with (a peripheral recess formed therein, the segments of a split ring [9 which offers support to the inner edge of the ring die 9.

A die block 2| carried on the nut, forms with the die, the floor of a compression chamber into which the loose pellet material is fed for extrusion through the die.

Such extrusion of the pellet material is accomplished through the use of compression means such as a pair of compression rollers 23 journalled 'in a spider adapted for rotation about the sleeve H as an axis. The rollers and spider are enclosed by a spider housing 25 which supports centrally thereof, the aforementioned thrust bearing 13, and connects with the main drive shaft 21 of the mill which extends upwardly along the longitudinal axis of the mill to suitable power drive means.

The upper structure of the mill, which for simplicitys sake, has not been illustrated, may be of any desired construction, but preferably as illustrated in the patent to Edgar T. Meakin No. 2,065,141 of December 22, 1936, or the patent to Edgar N. Meakin No. 2,075,450, of March 30, 1937. Such structure, however, is incidental to the present invention.

Extending from the end of the main drive shaft downward axially of the sleeve II and spaced therefrom by suitable seals, is a knife shaft 29 which carries at its lower end, a bracket 3i for supporting a pair of diametrically disposed scraper knives 33 against the lower or discharge surface of the die ring. This type of knife is conventional structure in pellet mills, and functions in a conventional mill to produce pellets from the extruded strings of pellet material, as the knives are moved along the discharge surface of the die simultaneously with movement of the rollers, both being controlled by rotation of the main drive shaft in the type machine depicted in Figure 1.

The operating area of the die is the path traversed thereover by the rollers. Difficulty has been experienced in previous machines of this type in realizing uniform extrusion results transversely of the path, the difliculty residing in the fact that the pellets formed from the holes at the inner and outer peripheries were shorter and irregular.

In accordance with the present invention, I embody in such machine, means which will present a low wall bordering along the inner and outer peripheries of such path, the important consideration being that such wall shall rise from the compression surface of the die in proximity to the rollers at all times.

One manner of securing these requirements, is to provide a ring 35 of metal on the surface of the die bordering the outer periphery of the roller path and a similar ring 31 bordering the inner periphery of such path. The outer ring may be clamped in position between the upper surface of the die and the inner edge or'lip of the bowl, and the inner ring by rabbeting the peripheral edge of the die block and fastening the ring therein by machine screws or bolts, the ring having sufficient width to overhang the inner periphery of the die to the required extent.

These rings may be economically fabricated by forming the same of arcuate sections which may be interlocked or dovetailed, and these sections are preferably welded together to produce a unitary ring.

I have found that the inclusion of these rings .in the mill structure not only permit of the realization of uniformity of output across the die,

but in doing so, can enhance the output of the mill to the unexpected extent of around 65% as previously indicated, and at the same time pro .ducing uniform wear on the die and increasing .its life expectancy. The die hole pattern involving holes laid out in concentric circles over the face of the die seems to bring about the greatest increase in output with the use of the aforementioned rings. This is probably attributable to the fact that such pattern includes a larger percentage or" peripheral holes.

While I am not at this time prepared to state with certainty the reason for this unexpected increase in the mill output, with its other advantages, resulting from the inclusion of the peripheral rings in the mill assembly, it is believed that the rollers normally tend to squeeze the material out from between the die surface and the engaging portion of the rollers in addition to throwing the material toward the side of the bowl by centrifugal force, and that the rings tend to resist such squeezing and throwing out of the material, thereby causing the die holes along the inner and outer peripheries of the roller path to assume their full share of the load.

While the die bowl or the die might conceivably be formed to provide such a bordering wall alongside each edge of the roller path, such means of accomplishing the purpose of the present invention would not be practical.

By utilizing independent rings, the same can be made of material which will better withstand the abrasive action of the material to be extruded, and can be removably secured in place, whereby upon being worn to a point where they lose their efiiciency, or effectiveness to perform in their intended manner, the rings may be turned over and again used. When they are no longer effective, they may be discarded and replaced with similar rings, which from an economic standpoint, may be fabricated rather inexpensively.

While I have disclosed the preferred form or my invention as embodied in a specific type of pellet mill, the same is applicable to other types of mills, the essential requirement being the presence ofa means bordering the extrusion path on the die for resistin the spread of material from under the compression means.

Accordingly, I do not desire to be limited in my protection to the details of the invention as disclosed, except as may be necessitated by the appended claim.

I claim:

In combination, a circular bowl, a bowl floor including a centrally disposed die block and a ring die surrounding the same, said ring die having a plurality of holes thercthrcugh defining a circular extrusion path along the compression surface of die, and said bowl having an edge extending over the radial surface of said die, a ring disposed along the radial surface of said die beneath said die bowl edge and bordering said path along the outer circumference thereof, means removably clamping said bowl die together-with said ring clamped between them, a

second ring, said second ring having an outer circumferential edge bordering on the inner circumferential edge of said extrusion path and a radial width extending onto said die block, and means affixing said second ring to die block.

EDGAR N. MEAKEN References Cited in the file of this patent UNITED STATES PATENTS 

